In adults, blood pressure readings of 120/80 mmHg (millimeters of mercury) or lower are considered healthy. Study participants’ average blood pressure was 133/82 mmHg with sham filters, 129.5/80.2 with low-efficiency air filters and 130.7/81.9 with HEPA filters.

One limitation of the study is that it was too small to detect meaningful differences in blood pressure based on the type of air filters used, the authors note. The study also didn’t track people to see if they actually developed or died from cardiovascular diseases.

Even so, air filters may be a simple way to reduce the negative health effects of exposure to fine particulate matter, said Shohreh Farzan, an environmental health researcher at the Keck School of Medicine at the University of Southern California in Los Angeles who wasn’t involved in the study. Relatively small reductions in blood pressure can improve cardiovascular health, Farzan said by email.

Consumers should look for HEPA filters that also have activated carbon filters and are certified by the Association of Home Appliance Manufacturers (AHAM), said Kai-Jen Chuang, a public health researcher at Taipei Medical University in Taiwan who wasn’t involved in the study.